1 /* 2 * i2c-smbus.c - SMBus extensions to the I2C protocol 3 * 4 * Copyright (C) 2008 David Brownell 5 * Copyright (C) 2010 Jean Delvare <jdelvare@suse.de> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 */ 17 18 #include <linux/device.h> 19 #include <linux/i2c.h> 20 #include <linux/i2c-smbus.h> 21 #include <linux/interrupt.h> 22 #include <linux/kernel.h> 23 #include <linux/module.h> 24 #include <linux/slab.h> 25 #include <linux/workqueue.h> 26 27 struct i2c_smbus_alert { 28 unsigned int alert_edge_triggered:1; 29 int irq; 30 struct work_struct alert; 31 struct i2c_client *ara; /* Alert response address */ 32 }; 33 34 struct alert_data { 35 unsigned short addr; 36 u8 flag:1; 37 }; 38 39 /* If this is the alerting device, notify its driver */ 40 static int smbus_do_alert(struct device *dev, void *addrp) 41 { 42 struct i2c_client *client = i2c_verify_client(dev); 43 struct alert_data *data = addrp; 44 struct i2c_driver *driver; 45 46 if (!client || client->addr != data->addr) 47 return 0; 48 if (client->flags & I2C_CLIENT_TEN) 49 return 0; 50 51 /* 52 * Drivers should either disable alerts, or provide at least 53 * a minimal handler. Lock so the driver won't change. 54 */ 55 device_lock(dev); 56 if (client->dev.driver) { 57 driver = to_i2c_driver(client->dev.driver); 58 if (driver->alert) 59 driver->alert(client, data->flag); 60 else 61 dev_warn(&client->dev, "no driver alert()!\n"); 62 } else 63 dev_dbg(&client->dev, "alert with no driver\n"); 64 device_unlock(dev); 65 66 /* Stop iterating after we find the device */ 67 return -EBUSY; 68 } 69 70 /* 71 * The alert IRQ handler needs to hand work off to a task which can issue 72 * SMBus calls, because those sleeping calls can't be made in IRQ context. 73 */ 74 static void smbus_alert(struct work_struct *work) 75 { 76 struct i2c_smbus_alert *alert; 77 struct i2c_client *ara; 78 unsigned short prev_addr = 0; /* Not a valid address */ 79 80 alert = container_of(work, struct i2c_smbus_alert, alert); 81 ara = alert->ara; 82 83 for (;;) { 84 s32 status; 85 struct alert_data data; 86 87 /* 88 * Devices with pending alerts reply in address order, low 89 * to high, because of slave transmit arbitration. After 90 * responding, an SMBus device stops asserting SMBALERT#. 91 * 92 * Note that SMBus 2.0 reserves 10-bit addresses for future 93 * use. We neither handle them, nor try to use PEC here. 94 */ 95 status = i2c_smbus_read_byte(ara); 96 if (status < 0) 97 break; 98 99 data.flag = status & 1; 100 data.addr = status >> 1; 101 102 if (data.addr == prev_addr) { 103 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev " 104 "0x%02x, skipping\n", data.addr); 105 break; 106 } 107 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n", 108 data.addr, data.flag); 109 110 /* Notify driver for the device which issued the alert */ 111 device_for_each_child(&ara->adapter->dev, &data, 112 smbus_do_alert); 113 prev_addr = data.addr; 114 } 115 116 /* We handled all alerts; re-enable level-triggered IRQs */ 117 if (!alert->alert_edge_triggered) 118 enable_irq(alert->irq); 119 } 120 121 static irqreturn_t smbalert_irq(int irq, void *d) 122 { 123 struct i2c_smbus_alert *alert = d; 124 125 /* Disable level-triggered IRQs until we handle them */ 126 if (!alert->alert_edge_triggered) 127 disable_irq_nosync(irq); 128 129 schedule_work(&alert->alert); 130 return IRQ_HANDLED; 131 } 132 133 /* Setup SMBALERT# infrastructure */ 134 static int smbalert_probe(struct i2c_client *ara, 135 const struct i2c_device_id *id) 136 { 137 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev); 138 struct i2c_smbus_alert *alert; 139 struct i2c_adapter *adapter = ara->adapter; 140 int res; 141 142 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert), 143 GFP_KERNEL); 144 if (!alert) 145 return -ENOMEM; 146 147 alert->alert_edge_triggered = setup->alert_edge_triggered; 148 alert->irq = setup->irq; 149 INIT_WORK(&alert->alert, smbus_alert); 150 alert->ara = ara; 151 152 if (setup->irq > 0) { 153 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq, 154 0, "smbus_alert", alert); 155 if (res) 156 return res; 157 } 158 159 i2c_set_clientdata(ara, alert); 160 dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n", 161 setup->alert_edge_triggered ? "edge" : "level"); 162 163 return 0; 164 } 165 166 /* IRQ and memory resources are managed so they are freed automatically */ 167 static int smbalert_remove(struct i2c_client *ara) 168 { 169 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 170 171 cancel_work_sync(&alert->alert); 172 return 0; 173 } 174 175 static const struct i2c_device_id smbalert_ids[] = { 176 { "smbus_alert", 0 }, 177 { /* LIST END */ } 178 }; 179 MODULE_DEVICE_TABLE(i2c, smbalert_ids); 180 181 static struct i2c_driver smbalert_driver = { 182 .driver = { 183 .name = "smbus_alert", 184 }, 185 .probe = smbalert_probe, 186 .remove = smbalert_remove, 187 .id_table = smbalert_ids, 188 }; 189 190 /** 191 * i2c_setup_smbus_alert - Setup SMBus alert support 192 * @adapter: the target adapter 193 * @setup: setup data for the SMBus alert handler 194 * Context: can sleep 195 * 196 * Setup handling of the SMBus alert protocol on a given I2C bus segment. 197 * 198 * Handling can be done either through our IRQ handler, or by the 199 * adapter (from its handler, periodic polling, or whatever). 200 * 201 * NOTE that if we manage the IRQ, we *MUST* know if it's level or 202 * edge triggered in order to hand it to the workqueue correctly. 203 * If triggering the alert seems to wedge the system, you probably 204 * should have said it's level triggered. 205 * 206 * This returns the ara client, which should be saved for later use with 207 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL 208 * to indicate an error. 209 */ 210 struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter, 211 struct i2c_smbus_alert_setup *setup) 212 { 213 struct i2c_board_info ara_board_info = { 214 I2C_BOARD_INFO("smbus_alert", 0x0c), 215 .platform_data = setup, 216 }; 217 218 return i2c_new_device(adapter, &ara_board_info); 219 } 220 EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert); 221 222 /** 223 * i2c_handle_smbus_alert - Handle an SMBus alert 224 * @ara: the ARA client on the relevant adapter 225 * Context: can't sleep 226 * 227 * Helper function to be called from an I2C bus driver's interrupt 228 * handler. It will schedule the alert work, in turn calling the 229 * corresponding I2C device driver's alert function. 230 * 231 * It is assumed that ara is a valid i2c client previously returned by 232 * i2c_setup_smbus_alert(). 233 */ 234 int i2c_handle_smbus_alert(struct i2c_client *ara) 235 { 236 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara); 237 238 return schedule_work(&alert->alert); 239 } 240 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert); 241 242 module_i2c_driver(smbalert_driver); 243 244 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>"); 245 MODULE_DESCRIPTION("SMBus protocol extensions support"); 246 MODULE_LICENSE("GPL"); 247